I assume you mean this:

https://en.wikipedia.org/wiki/Craigslist_Inc._v._3Taps_Inc.

It seems unlikely to apply to a Chrome extension:

Craigslist Inc. v. 3Taps Inc., 942 F.Supp.2d 962 (N.D. Cal. 2013) was a Northern District of California Court case in which the court held that sending a cease-and-desist letter and enacting an IP address block is sufficient notice of online trespassing, which a plaintiff can use to claim a violation of the Computer Fraud and Abuse Act.

What would keep it from applying to an extension? It says sufficient, not necessary and sufficient.

For one thing, the extension author is not an active participant and cannot be considered to be trespassing. A user, maybe. But I don't think we'll see Slack banning users anytime soon.

The intent is clear. I don't know the details of those decisions but Blizzard has won cases and stopped people from distributing tools that access their services in ways they don't approve of.

There may be other laws, precedents, and circumstances that are relevant. That doesn't mean that this case is.